Beware that Exploding Custard Powder!!

About 5 or 6 years ago  I was working in the Chemical Industry investigating the dust explosion properties of various organic chemical powders used in the agricultural research industry.

On reading a current copy of the New Scientist, I noticed that  somebody had written in to the magazine posing the question:

“Can someone explain why certain types of dust, for example brick dust and custard powder are explosive”?

My reply to this was:

Brick dust cannot form an explosive dust as it is inorganic and  in a fully oxidised state. The only inorganic materials which can explode are elements for example;  magnesium, sulphur and aluminium. These do form explosive dusts because they are oxidised rapidly when in a finely divided state (i.e. a dust)

Organic dusts such as custard powder, icing sugar, flour, coffee, dust in grain silos, and coal dust, just to give a few examples; can however explode violently under certain conditions. The material has to be a fine dust cloud in a confined space and in the right concentration, then when a source of ignition is applied, the dust can explode violently.

The consequences of such dust explosions in industry have been severe with many deaths and destroyed plants.

Ian Iosson